Some conventional air conditioning systems utilize an indoor evaporator and an outdoor condenser. In conjunction with an expansion device, the outdoor condenser is used to rapidly lower the temperature of the refrigerant that is subsequently used to cool air of an indoor area. The refrigerant is heated with warm indoor air of the indoor area within the evaporator and then drawn into a compressor for circulating back to the condenser. Placement of the condenser outdoors allows heat from the refrigerant to be discharged to outdoor air.
Such systems often include a hot gas reheat circuit that is used to remove humidity from the conditioned air within the cooled space without providing additional cooling. Such conditions often arise on cool, rainy days in the springtime or autumn. The hot gas reheat circuit includes an indoor reheat coil that is located in the path of air exiting the evaporator. As such, the air is passed through the evaporator to remove humidity and to be cooled, while the reheat coil warms the air back to the temperature of the indoor area.
In order to maintain the proper temperature and humidity within the indoor space, one or more valves are used divide flow of refrigerant from the compressor between the outdoor condenser and the indoor reheat coil. These valves are typically operated in an on-off manner to split flow between the condenser and reheat coil with the addition of various bypass circuits. One such system, described in U.S. Pat. No. 7,219,505 to Weber et al., discloses the additional use of solenoid valves to exchange refrigerant between the reheat circuit and the cooling circuit in order to control refrigerant flow through the reheat circuit. Similarly, U.S. Patent Application Pub. No. 2011/0154837 to Taras discloses the use of pulse width modulation of solenoid valves to control reheat refrigerant flow. Both of these systems, however, merely set mechanical limits to the system and control reheat flow by diverting refrigerant through the additional bypass piping with on-off valves.